Diamine compound, and polyimide compound and molded product using the same

ABSTRACT

[Problems to be solved] The present invention provides a novel diamine compound which allows for the synthesis of a polyimide compound having a high solubility in an organic solvent and a high melt moldability.[Solution] The diamine compound according to the present invention is characterized by being represented by the following general formula (1):(whereinR1 to R8 are each independently selected from the group consisting of a hydrogen atom, a fluorine atom, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted aromatic group; and at least one of R1 to R8 is a substituted or unsubstituted aromatic group).

RELATED APPLICATION DATA

This application is a divisional application which claims priority toU.S. patent application Ser. No. 16/481,090, filed on Jul. 26, 2019,which is a National Stage Application under 35 U.S.C. 371 of co-pendingPCT application number PCT/JP2018/001205 designating the United Statesand filed Jan. 17, 2018; which claims the benefit of JP application no.2017-013580, filed Jan. 27, 2017, JP application no. 2017-013567, filedJan. 27, 2017, JP application no. 2017-226250, filed Nov. 24, 2017, andJP application no. 2017-226242, filed Nov. 24, 2017 each of which arehereby incorporated by reference in their entireties.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a novel diamine compound. Moreparticularly, the present invention relates to a novel diamine compoundwhich allows for the synthesis of a polyimide compound having animproved solubility in an organic solvent and an improved meltmoldability; as well as to a polyimide compound synthesized using thesame; and a molded product including the polyimide compound.

Background Art

In general, polyimide compounds have an excellent mechanical strength,wear resistance, dimensional stability, chemical resistance, electricalinsulation properties and the like, in addition to having a high heatresistance, and thus are widely used in the field of electronicmaterials, such as flexible printed circuit boards and printed wiringboards. In addition to the field of electronic devices, polyimidecompounds are also widely used in the fields of space and aviation,automobiles and the like. Among these polyimide compounds, polyimidecompounds formed from an aromatic diamine and an aromatic acidanhydride, as raw materials, are known to have an excellent mechanicalstrength and heat resistance. For example, a polyimide compound formedfrom an aromatic diamine, such as 4-aminophenyl-4-aminobenzoate, andpyromellitic dianhydride, as raw materials, has an excellent heatresistance, mechanical properties, electrical insulation and the like,and is suitably used as a protective material or an insulating materialin the field of electronic devices (see, for example, Patent Document1).

However, the above described aromatic polyimide compound has a lowsolubility in an organic solvent, due to having a rigid structure.Therefore, in the case of producing a cover film for a flexible printedwiring substrate (FPC), an insulating layer for an electronic circuit orthe like, the production thereof has been carried out, not by using thepolyimide compound, but by the following method. Specifically, theproduction has been carried out by allowing a diamine compound to reactwith an acid anhydride in an organic solvent, to obtain a polyamic acidsolvent which contains a polyamic acid having a high solubility in anorganic solvent, and coating the resulting solvent on a substrate or thelike, followed by heat drying at a high temperature to allow acyclodehydration reaction (polyimidization) to occur (see, for example,Patent Document 1).

PRIOR ART DOCUMENT Patent Document

Patent Document 1: JP 2014-173071 A

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, the substrate on which a polyimide film is to be formed needsto have a high heat resistance capable of withstanding thecyclodehydration reaction (withstanding a temperature of from 300 to400° C., in general). Further, such a production must be carried outunder an environment where a special heating apparatus for carrying outthe cyclodehydration reaction can be used. Thus, there are variouslimitations in the production of a molded article using a polyimidecompound. In addition, polyamic acid compounds have problems that theyare unstable, react with water, are easily hydrolyzed, and aresusceptible to a decrease in molecular weight.

Moreover, most of polyimide compounds do not have a melting point, andeven those having a melting point have a very low melting point, makingit difficult to carry out melt molding. Therefore, there is also aproblem in melt moldability.

The present invention has been made in view of the above describedproblems. An object of the present invention is to provide: a noveldiamine compound which allows for the synthesis of a polyimide compoundhaving a high solubility in an organic solvent and a high meltmoldability; and a method of synthesizing the diamine compound.

Another object of the present invention is to provide a polyimidecompound having a high solubility in an organic solvent and a high meltmoldability, which is synthesized using the above described diaminecompound.

Still another object of the present invention is to provide a moldedproduct, such as, for example, a polyimide film, which includes theabove described polyimide compound, and which has a heat resistance andmechanical properties comparable to a polyimide film including aconventional polyimide compound.

Means for Solving the Problems

The diamine compound according to the present invention is characterizedby being represented by the following general formula (1):

(wherein

R₁ to R₈ are each independently selected from the group consisting of ahydrogen atom, a fluorine atom, a substituted or unsubstituted alkylgroup, and a substituted or unsubstituted aromatic group; and at leastone of R₁ to R₈ is a substituted or unsubstituted aromatic group).

In the above described embodiment, at least one or two of R₅ to R₈is/are (each) preferably a substituted or unsubstituted aromatic group.

In the above described embodiment, one or two of R₅ to R₈ is/are (each)preferably a substituted or unsubstituted aromatic group, and R₁ to R₈other than the aromatic group(s) are each preferably selected from thegroup consisting of a hydrogen atom, a fluorine atom, and a substitutedor unsubstituted alkyl group.

In the above described embodiment, the substituted or unsubstitutedaromatic group preferably has from 5 to 20 carbon atoms.

In the above described embodiment, the substituted or unsubstitutedaromatic group is preferably selected from the group consisting of aphenyl group, a methylphenyl group, a phenoxy group, a benzyl group anda benzyloxy group.

The method of synthesizing the diamine compound according to the presentinvention includes the steps of:

allowing a compound represented by the following general formula (3):

to react with a compound represented by the following general formula(4):

to obtain a reaction product; and

reducing the nitro group in the reaction product

(wherein

R₁ to R₈ are each independently selected from the group consisting of ahydrogen atom, a fluorine atom, a substituted or unsubstituted alkylgroup, and a substituted or unsubstituted aromatic group;

at least one of R₁ to R₈ is a substituted or unsubstituted aromaticgroup;

R₁′ to R₈′ are each independently selected from the group consisting ofa hydrogen atom, a fluorine atom, a substituted or unsubstituted alkylgroup, and a substituted or unsubstituted aromatic group; and

at least one of R₁′ to R₈′ is an aromatic group).

The polyimide compound according to the present invention ischaracterized by being a reaction product of the above described diaminecompound with an acid anhydride.

In the above described embodiment, the acid anhydride is preferablyrepresented by the following general formula(e) (8) and/or (9):

(wherein

L₁ represents a linking group selected from the following group oflinking groups:

wherein

R₉ to R₂₀ are each independently selected from the group consisting of ahydrogen atom, a substituted alkyl group and an unsubstituted alkylgroup; and * represents a binding position).

In the above described embodiment, the acid anhydride is preferablyrepresented by the following general formula(e) (8) and/or (9):

wherein

L₁ represents a linking group selected from the following group oflinking groups:

wherein

X represents a halogen group selected from a fluoro group, a chlorogroup, a bromo group and an iodo group;

R₂₁ to R₃₀ are each independently selected from the group consisting ofa hydrogen atom, a substituted alkyl group and an unsubstituted alkylgroup; and

* represents a binding position).

The molded product according to the present invention is characterizedby including the above described polyimide compound.

Effect of the Invention

The diamine compound according to the present invention enables tomarkedly improve the solubility in an organic solvent and the meltmoldability of a polyimide compound synthesized using the diaminecompound, and to produce a molded article of the polyimide compoundwithout taking into consideration the heat resistance or the like of thesubstrate to be used therefor.

Further, it becomes possible to produce the molded article in variousplaces, since there is no need to use a special apparatus for carryingout a heat treatment, in the production of the molded article.

Still further, the molded product according to the present invention hasa 5% by weight reduction ratio, a glass transition temperature (Tg), amelting temperature, a thermal expansion coefficient, a tensilestrength, an elastic modulus and a water absorption rate, which arecomparable to those of a molded product produced using a conventionalpolyimide compound, as well as a high heat resistance and highmechanical properties. Therefore, the molded product according to thepresent invention can be used in various fields, such as the fields of:electronic devices, space and aviation, automobiles, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a ¹H-NMR chart of a compound obtained in Examples andrepresented by chemical formula (2).

FIG. 2 is a ¹³C-NMR chart of the compound obtained in Examples andrepresented by the chemical formula (2).

FIG. 3 is an FT-IR chart of the compound obtained in Examples andrepresented by the chemical formula (2).

DETAILED DESCRIPTION OF THE INVENTION Diamine Compound

The diamine compound according to the present invention is characterizedby being represented by the following general formula (1):

In the above described formula, R₁ to R₈ are each independently selectedfrom the group consisting of a hydrogen atom, a fluorine atom, asubstituted or unsubstituted alkyl group, and a substituted orunsubstituted aromatic group; and at least one of R₁ to R₈ is anaromatic group. Preferably, one or two of R₁ to R₈ is/are (each) anaromatic group.

Preferably, one or two of R₅ to R₈ is/are (each) a substituted orunsubstituted aromatic group, and more preferably, at least R₅ or R₇ isan aromatic group.

When the diamine compound has an aromatic group(s) at the abovedescribed position(s), the steric hindrance of the diamine compound canbe reduced, as a result of which a polymerization reaction with an acidanhydride or the like can be carried out in a favorable manner.

In a particularly preferred embodiment, one or two of R₅ to R₈ is/are(each) a substituted or unsubstituted aromatic group, and R₁ to R₈ otherthan the aromatic group(s) are each selected from the group consistingof a hydrogen atom, a fluorine atom, and a substituted or unsubstitutedalkyl group. Specific examples include a compound represented by thefollowing formula (2) (an embodiment in which R₇ is an aromatic group;and R₁ to R₆ and R₈ other than R₇ are each a hydrogen atom).

In the present invention, the definition of the alkyl group includes alinear alkyl group, a branched alkyl group and a cyclic alkyl group.Further, an alkoxy group and an alkylamino group, each of which binds tothe main skeleton via an oxygen atom or a nitrogen atom, is alsoincluded in the definition.

Likewise, the definition of the aromatic group includes a substituentwhich binds to the main skeleton via an oxygen atom, a nitrogen atom, ora carbon atom. Further, the definition of the aromatic group furtherincludes a heteroaromatic group, such as pyrrole group.

The alkyl group and the aromatic group are preferably unsubstituted,from the viewpoint of facilitating the synthesis of the diamine compoundaccording to the present invention, and the application of the compoundin the field of electronic component materials. However, the alkyl groupand the aromatic group may have a substituent, and examples of thesubstituent include: alkyl groups; halogen groups such as fluoro groupand chloro group; amino group; nitro group; hydroxyl group; cyano group;carboxyl group; and sulfonic acid group. The alkyl group and thearomatic group may be a group having one or more, or two or more ofthese substituents.

The alkyl group preferably has from 1 to 10 carbon atoms, and morepreferably from 1 to 3 carbon atoms.

Examples of the alkyl group having from 1 to 10 carbon atoms include:methyl group, ethyl group, n-propyl group, isopropyl group, n-butylgroup, tert-butyl group, n-pentyl group, sec-pentyl group, n-hexylgroup, cyclohexyl group, n-heptyl group, n-octyl group, n-nonyl group,n-decyl group, fluoromethyl group, difluoromethyl group, trifluoromethylgroup, chloromethyl group, dichloromethyl group, trichloromethyl group,bromomethyl group, dibromomethyl group, tribromomethyl group,fluoroethyl group, difluoroethyl group, trifluoroethyl group,chloroethyl group, dichloroethyl group, trichloroethyl group, bromoethylgroup, dibromoethyl group, tribromoethyl group, hydroxymethyl group,hydroxyethyl group, hydroxylpropyl group, methoxy group, ethoxy group,n-propoxy group, n-butoxy group, n-pentyloxy group, sec-pentyloxy group,n-hexyloxy group, cyclohexyloxy group, n-heptyloxy group, n-octyloxygroup, n-nonyloxy group, n-decyloxy group, trifluoromethoxy group,methylamino group, dimethylamino group, trimethylamino group, ethylaminogroup, and propylamino group.

Among the above described alkyl groups, methyl group, ethyl group,methoxy group, ethoxy group and trifluoromethyl group are preferred,from the viewpoint of steric hindrance and heat resistance.

The aromatic group preferably has from 5 to 20 carbon atoms, and morepreferably from 6 to 10 carbon atoms.

Examples of the aromatic group having from 5 to 20 carbon atoms include:phenyl group, tolyl group, methylphenyl group, dimethylphenyl group,ethylphenyl group, diethylphenyl group, propylphenyl group, butylphenylgroup, fluorophenyl group, pentafluorophenyl group, chlorphenyl group,bromophenyl group, methoxyphenyl group, dimethoxyphenyl group,ethoxyphenyl group, diethoxyphenyl group, benzyl group, methoxybenzylgroup, dimethoxybenzyl group, ethoxybenzyl group, diethoxybenzyl group,aminophenyl group, aminobenzyl group, nitrophenyl group, nitrobenzylgroup, cyanophenyl group, cyanobenzyl group, phenethyl group,phenylpropyl group, phenoxy group, benzyloxy group, phenylamino group,diphenylamino group, biphenyl group, naphthyl group, phenylnaphthylgroup, diphenylnaphthyl group, anthryl group, anthrylphenyl group,phenylanthryl group, naphthacenyl group, phenanthryl group,phenanthrylphenyl group, phenylphenanthryl group, pyrenyl group,phenylpyrenyl group, fluorenyl group, phenylfluorenyl group,naphthylethyl group, naphthylpropyl group, anthracenylethyl group, andphenanthrylethyl group; and heteroaromatic groups such as pyrrole group,imidazole group, thiazole group, oxazole group, furan group, thiophenegroup, triazole group, pyrazole group, isoxazole group, isothiazolegroup, pyridine group, pyrimidine group, benzofuran group,benzothiophene group, quinolone group, isoquinolone group, indolylgroup, benzothiazolyl group, and carbazolyl group.

Among the above described aromatic groups, phenyl group, phenoxy group,benzyl group and benzyloxy group are preferred, from the viewpoint ofthe availability of starting raw materials and the cost of synthesis.

Method of Synthesizing Diamine Compound

The diamine compound according to the present invention can be obtainedby allowing a compound represented by the following general formula (3):

to react with a compound represented by the following general formula(4):

and then reducing the nitro group.

In the above described formulae, R₁′ to R₈′ are each independentlyselected from the group consisting of a hydrogen atom, a substituted orunsubstituted alkyl group, and a substituted or unsubstituted aromaticgroup; and at least one of R₁′ to R₈′ is an aromatic group.

Preferably, at least one of R₅′ to R₈′ is a substituted or unsubstitutedaromatic group, and more preferably, at least R₅′ or R₇′ is an aromaticgroup.

In a particularly preferred embodiment, one of R₅′ to R₈′ is asubstituted or unsubstituted aromatic group, and R₁′ to R₈′ other thanthe aromatic group are each a hydrogen atom.

Further, in the above described formula (3), X represents a hydroxylgroup, or a halogen group selected from a fluoro group, a chloro group,a bromo group and an iodo group. From the viewpoint of the reactivitywith the compound represented by the general formula (4), X ispreferably a halogen group, and particularly preferably a chloro groupor a bromo group.

In cases where X in the general formula (3) is a hydroxyl group, thereaction of the compound represented by the general formula (3) with thecompound represented by general formula (4) is preferably carried out inthe presence of a catalyst or a dehydration condensation agent.

Examples of the catalyst include: organic and inorganic basic compoundssuch as dimethylamino pyridine, tri-n-butylamine, pyridine, lysine,imidazole, sodium carbonate, sodium alcoholate and potassium hydrogencarbonate; organic acids such as toluenesulfonic acid, methanesulfonicacid and sulfuric acid; and inorganic acids.

Examples of the dehydration condensation agent include: carbodiimidessuch as N,N′-dicyclohexylcarbodiimide (DCC),N,N′-diisopropylcarbodiimide andN-cyclohexyl-N′-(4-diethylamino)cyclohexylcarbodiimide.

Further, in cases where X in the general formula (3) is a halogen group,the reaction of the compound represented by the general formula (3) withthe compound represented by general formula (4) is preferably carriedout in the presence of an acid acceptor. Specific examples of the acidacceptor include: trialkylamines such as triethylamine, tributylamineand N,N-dimethylcyclohexylamine; aliphatic cyclic tertiary amines suchas N-methylmorpholine; aromatic amines such as N,N-dimethylaniline andtriphenylamine; and heterocyclic amines such as pyridine, picoline,lutidine and quinolone.

More specifically, the diamine compound represented by the abovedescribed formula (2) can be obtained by allowing a compound representedby the following formula (5):

to react with a compound represented by the formula (6):

The compound represented by the general formula (4) can be obtained bynitration of a compound represented by the following general formula (7)which is commercially available or synthesized. The nitration of thecompound represented by the following general formula (7) can be carriedout by a conventionally known nitration method, using a mixed acid ofconcentrated sulfuric acid and concentrated nitric acid, nitric acid,fuming nitric acid, an acid alkali metal salt in concentrated sulfuricacid, acetyl nitrate, a nitronium salt, a nitrogen oxide and the like.

R₅″ to R₈″ are each independently selected from the group consisting ofa hydrogen atom, a substituted or unsubstituted alkyl group, and asubstituted or unsubstituted aromatic group. Preferably, at least one ofR₅″ to R₈″ is an aromatic group, and more preferably one or two of R₅″to R₈″ is/are (each) an aromatic group.

The diamine compound according to the present invention can also be usedin the synthesis of a compound other than the polyimide compound to bedescribed later.

For example, it is possible to synthesize a polyamide compound byreacting the diamine compound with: terephthalic acid, isophthalic acid,naphthalenedicarboxylic acid, diphenyl ether carboxylic acid,diphenylsulfonecarboxylic acid, biphenyldicarboxylic acid,terphenyldicarboxylic acid, diphenylmethanedicarboxylic acid,2,2-bis(4-carboxyphenyl)propane,2,2-bis(4-carboxyphenyl)hexafluoropropane, cyclohexanedicarboxylic acidor dicyclohexanedicarboxylic acid, or with a dicarboxylic acidderivative such as an acid halide thereof.

Further, the diamine compound according to the present invention canalso be used in the synthesis of a polyamideimide compound, apolyurethane compound, or an epoxy compound.

Polyimide Compound

The polyimide compound according to the present invention is a reactionproduct of the diamine compound represented by the above describedgeneral formula (1) with an acid anhydride. The structure of the diaminecompound represented by the general formula (1) has already beendescribed above, and is thus omitted here.

When the diamine compound represented by the above described generalformula (1) is used as a component of the polyimide compound, it ispossible to markedly improve the solubility of the polyimide compound inan organic solvent.

In the polyimide compound according to the present invention, thecontent of the diamine compound represented by the above describedgeneral formula (1) in the total diamine components is preferably from10% by mole to 100% by mole, more preferably from 30% by mole to 100% bymole, and still more preferably from 50% by mole to 100% by mole. Whenthe content of the diamine compound is adjusted within the abovedescribed numerical range, it is possible to introduce a rigid esterstructure into the resulting polyimide compound, and to further improvethe solubility of the polyimide compound in an organic solvent.

The polyimide compound according to the present invention preferably hasa number average molecular weight of from 2,000 to 200,000, and morepreferably from 4,000 to 100,000.

In the present invention, the number average molecular weight refers toa molecular weight in terms of polystyrene, which is obtained based on acalibration curve prepared by a gel permeation chromatography (GPC)apparatus, using standard polystyrene.

When the number average molecular weight is adjusted within the abovedescribed numerical range, it is possible to improve the mechanicalproperties of a film obtained using the resulting polyimide compound, aswell as to improve the moldability of the polyimide compound.

The polyimide compound according to the present invention preferably hasa melting point of 150° C. or higher and 420° C. or lower, morepreferably 200° C. or higher and 350° C. or lower, from the viewpoint ofimproving the heat resistance of the resulting molded product, as wellas the productivity and the cost of the molded product.

Acid Anhydride

Examples of the acid anhydride include oxydiphthalic dianhydride,pyromellitic dianhydride, 3-fluoropyromellitic dianhydride,3,6-difluoropyromellitic dianhydride,3,6-bis(trifluoromethyl)pyromellitic dianhydride,1,2,3,4-benzenetetracarboxylic dianhydride,2,2′,3,3′-benzophenonetetracarboxylic dianhydride,3,3′,4,4′-benzophenonetetracarboxylic dianhydride,3,3′,4,4′-biphenyltetracarboxylic dianhydride,3,3′,4,4′-biphenylsulfonetetracarboxylic dianhydride,4,4′-(4,4′-isopropylidenediphenoxy)bisphthalic dianhydride,1,2,4,5-cyclohexanetetracarboxylic dianhydride,2,3,3′,4′-biphenyltetracarboxylic dianhydride,3,3″,4,4″-terphenyltetracarboxylic dianhydride,3,3′″,4,4″′-quaterphenyltetracarboxylic dianhydride,2,2′,3,3′-biphenyltetracarboxylic dianhydride, methylene-4,4′-diphthalicdianhydride, 1,1-ethynylidene-4,4′-diphthalic dianhydride,2,2-propylidene-4,4′-diphthalic dianhydride,1,2-ethylene-4,4′-diphthalic dianhydride,1,3-trimethylene-4,4′-diphthalic dianhydride,1,4-tetramethylene-4,4′-diphthalic dianhydride,1,5-pentamethylene-4,4′-diphthalic dianhydride,1,3-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride,1,4-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride,bis[3-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride,bis[4-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride,2,2-bis[3-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride,2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride,difluoromethylene-4,4′-diphthalic dianhydride,1,1,2,2-tetrafluoro-1,2-ethylene-4,4′-diphthalic dianhydride,3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride,oxy-4,4′-diphthalic dianhydride, bis(3,4-dicarboxyphenyl) etherdianhydride, thio-4,4′-diphthalic dianhydride, sulfonyl-4,4′-diphthalicdianhydride, 1,3-bis(3,4-dicarboxyphenyl)benzene dianhydride,1,4-bis(3,4-dicarboxyphenyl)benzene dianhydride,1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride,1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride,bis(3,4-dicarboxyphenoxy)dimethylsilane dianhydride,1,3-bis(3,4-dicarboxyphenoxy)-1,1,3,3-tetramethyldisiloxane dianhydride,2,3,6,7-naphthalenetetracarboxylic dianhydride,1,2,5,6-naphthalenetetracarboxylic dianhydride,3,4,9,10-perylenetetracarboxylic dianhydride,2,3,6,7-anthracenetetracarboxylic dianhydride,1,2,7,8-phenanthrenetetracarboxylic dianhydride,1,2,3,4-butanetetracarboxylic dianhydride,1,2,3,4-cyclobutanetetracarboxylic dianhydride,cyclopentanetetracarboxylic dianhydride,cyclohexane-1,2,3,4-tetracarboxylic dianhydride,cyclohexane-1,2,4,5-tetracarboxylic dianhydride,3,3′,4,4′-bicyclohexyltetracarboxylic dianhydride,carbonyl-4,4′-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride,methylene-4,4′-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride,1,2-ethylene-4,4′-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride,oxy-4,4′-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride,thio-4,4′-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride,sulfonyl-4,4′-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride,3,3′,5,5′-tetrakis(trifluoromethyl)oxy-4,4′-diphthalic dianhydride,3,3′,6,6′-tetrakis(trifluoromethyl)oxy-4,4′-diphthalic dianhydride,5,5′,6,6′-tetrakis(trifluoromethyl)oxy-4,4′-diphthalic dianhydride,3,3′,5,5′,6,6′-hexakis (trifluoromethyl)oxy-4,4′-diphthalic dianhydride,3,3′-difluorosulfonyl-4,4′-diphthalic dianhydride,5,5′-difluorosulfonyl-4,4′-diphthalic dianhydride,6,6′-difluorosulfonyl-4,4′-diphthalic dianhydride,3,3′,5,5′,6,6′-hexafluorosulfonyl-4,4′-diphthalic dianhydride,3,3′-bis(trifluoromethyl)sulfonyl-4,4′-diphthalic dianhydride,5,5′-bis(trifluoromethyl)sulfonyl-4,4′-diphthalic dianhydride,6,6′-bis(trifluoromethyl)sulfonyl-4,4′-diphthalic dianhydride,3,3′,5,5′-tetrakis(trifluoromethyl)sulfonyl-4,4′-diphthalic dianhydride,3,3′,6,6′-tetrakis(trifluoromethyl)sulfonyl-4,4′-diphthalic dianhydride,5,5′,6,6′-tetrakis(trifluoromethyl)sulfonyl-4,4′-diphthalic dianhydride,3,3′,5,5′,6,6′-hexakis (trifluoromethyl)sulfonyl-4,4′-diphthalicdianhydride, 3,3′-difluoro-2,2-perfluoropropylidene-4,4′-diphthalicdianhydride, 5,5′-difluoro-2,2-perfluoropropylidene-4,4′-diphthalicdianhydride, 6,6′-difluoro-2,2-perfluoropropylidene-4,4′-diphthalicdianhydride,3,3′,5,5′,6,6′-hexafluoro-2,2-perfluoropropylidene-4,4′-diphthalicdianhydride,3,3′-bis(trifluoromethyl)-2,2-perfluoropropylidene-4,4′-diphthalicdianhydride, and ethylene glycol bistrimellitate dianhydride.

Among the above described anhydrides, pyromellitic dianhydride,3,3′,4,4′-biphenyltetracarboxylic dianhydride,2,2-bis[3-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride,2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride and3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride,oxy-4,4′-diphthalic dianhydride are preferred, from the viewpoint ofimproving the reactivity with the diamine compound according to thepresent invention.

One kind, or two or more kinds of the above described anhydrides may beused in the synthesis of the polyimide compound according to the presentinvention.

In one embodiment, the polyimide compound according to the presentinvention is a reaction product of the diamine compound represented bythe above described general formula (1) with an acid anhydride(s)represented by the following general formula(e) (8) and/or (9):

In one embodiment, L₁ in the above described formulae represents alinking group selected from the following group of linking groups. Thepolyimide compound, which is a reaction product of an acid anhydridehaving a linking group selected from the following group of linkinggroups, with the diamine compound represented by the general formula(1), has a low melting temperature, and has an extremely excellent meltmoldability.

In the above described formulae,

R₉ to R₂₀ are each independently selected from the group consisting of ahydrogen atom, a substituted alkyl group and an unsubstituted alkylgroup; and * represents a binding position.

The alkyl group is preferably unsubstituted, from the viewpoint offacilitating the synthesis of the diamine compound according to thepresent invention, and the application of the compound in the field ofelectronic component materials. However, the alkyl group may have asubstituent, and examples of the substituent include: alkyl groups;halogen groups such as fluoro group and chloro group; amino group; nitrogroup; hydroxyl group; cyano group; carboxyl group; and sulfonic acidgroup. The alkyl group and the aromatic group may be a group having oneor more, or two or more of these substituents.

The alkyl group preferably has from 1 to 10 carbon atoms, and morepreferably from 1 to 3 carbon atoms.

Examples of the alkyl group having from 1 to 10 carbon atoms include:methyl group, ethyl group, n-propyl group, isopropyl group, n-butylgroup, tert-butyl group, n-pentyl group, sec-pentyl group, n-hexylgroup, cyclohexyl group, n-heptyl group, n-octyl group, n-nonyl group,n-decyl group, fluoromethyl group, difluoromethyl group, trifluoromethylgroup, chloromethyl group, dichloromethyl group, trichloromethyl group,bromomethyl group, dibromomethyl group, tribromomethyl group,fluoroethyl group, difluoroethyl group, trifluoroethyl group,chloroethyl group, dichloroethyl group, trichloroethyl group, bromoethylgroup, dibromoethyl group, tribromoethyl group, hydroxymethyl group,hydroxyethyl group, hydroxylpropyl group, methoxy group, ethoxy group,n-propoxy group, n-butoxy group, n-pentyloxy group, sec-pentyloxy group,n-hexyloxy group, cyclohexyloxy group, n-heptyloxy group, n-octyloxygroup, n-nonyloxy group, n-decyloxy group, trifluoromethoxy group,methylamino group, dimethylamino group, trimethylamino group, ethylaminogroup, and propylamino group.

Among the above described alkyl groups, methyl group, ethyl group,methoxy group, ethoxy group and trifluoromethyl group are preferred,from the viewpoint of steric hindrance and heat resistance.

From the viewpoint of improving the melt moldability of the polyimidecompound, L₁ is more preferably a linking group selected from thefollowing group of linking groups:

Accordingly, examples of the acid anhydride satisfying the generalformula (2) or (3) include the following compounds:

Further, in one embodiment, L₁ is a linking group selected from thefollowing group of linking groups. The polyimide compound, which is areaction product of an acid anhydride having a linking group selectedfrom the following group of linking groups, with the diamine compoundrepresented by the general formula (1), has an extremely high solubilityin an organic solvent.

In the above described formulae,

X represents a halogen group selected from a fluoro group, a chlorogroup, a bromo group and an iodo group; and is preferably a fluorogroup;

R₂₁ to R₃₀ are each independently selected from the group consisting ofa hydrogen atom, a substituted alkyl group and an unsubstituted alkylgroup; and

* represents a binding position.

The definition of the alkyl group is as described above.

From the viewpoint of improving the solubility in an organic solvent ofthe polyimide compound, L₁ is more preferably a linking group selectedfrom the following group of linking groups:

Accordingly, examples of the acid anhydride satisfying the generalformula (2) or (3) include the following compounds:

In the synthesis of the polyimide compound, two or more types of theacid anhydrides represented by the general formula(e) (8) and/or (9) maybe used.

Other Diamine Compounds

The polyimide compound according to the present invention may containanother diamine compound, in addition to the diamine compoundrepresented by the general formula (1).

Examples of the other diamine compound include m-phenylenediamine,p-phenylenediamine, 2,4-diaminotoluene,2,4(6)-diamino-3,5-diethyltoluene,5(6)-amino-1,3,3-trimethyl-1-(4-aminophenyl)-indan,4,4′-diamino-2,2′-dimethyl-1,1′-biphenyl,4,4′-diamino-2,2′-ditrifluoromethyl-1,1′-biphenyl,4,4′-diamino-3,3′-dimethyl-1,1′-biphenyl, 3,4′-diaminodiphenyl ether,4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl sulfone,4,4′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl sulfide,4-aminophenyl-4-aminobenzoate, 4,4′-(9-fluorenylidene)dianiline,9,9′-bis(3-methyl-4-aminophenyefluorene, 1,3-bis(3-aminophenoxy)benzene,1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene,2,2-bis(4-aminophenyl)propane, 2,2-bis(3-methyl-4-aminophenyl)propane,4,4′-(hexafluoroisopropylidene)dianiline,2,2-bis(3-amino-4-methylphenyl)hexafluoropropane,2,2-bis(3-methyl-4-aminophenyl)benzene,2,2-bis[4-(4-aminophenoxy)phenyl]propane,2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane,α,α-bis[4-(4-aminophenoxy)phenyl]-1,3-diisopropylbenzene,α,α-bis[4-(4-aminophenoxy)phenyl]-1,4-diisopropylbenzene,3,7-diamino-dimethyldibenzothiophene-5,5-dioxide,bis(3-carboxy-4-aminophenyl)methylene,3,3′-diamino-4,4′-dihydroxy-1,1′-biphenyl,4,4′-diamino-3,3′-dihydroxy-1,1′-biphenyl,2,2-bis(3-amino-4-hydroxyphenyl)propane,2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane,1,3-bis(3-hydroxy-4-aminophenoxy)benzene,2,2-bis(3-hydroxy-4-aminophenyl)benzene, and3,3′-diamino-4,4′-dihydroxydiphenylsulfone.

The polyimide compound according to the present invention may containone kind, or two or more kinds of the other diamine compounds describedabove, as a component(s).

The polyimide compound according to the present invention can be moldedinto a film or the like, as will be described later, and can be used asa base film or a cover film in a flexible printed wiring substrate(FPC). Further, the polyimide compound can also be used as an adhesiveagent in a flexible wiring substrate or the like.

In addition to the above, the polyimide compound can also be used as anelectrically insulating coating material for an electrical wire, a heatinsulating material, a transparent substrate for a liquid crystaldisplay element, a thin film transistor substrate or the like.

Method of Synthesizing Polyimide Compound

The polyimide compound according to the present invention can beproduced by a conventionally known method, using a diamine compoundrepresented by the above described general formula (1) and an acidanhydride. Specifically, the polyimide compound can be obtained byallowing the diamine compound to react with the acid anhydride to obtaina polyamide acid, and then carrying out a cyclodehydration reaction toconvert the polyamide acid into a polyimide compound.

The mixing ratio of the acid anhydride and the diamine compound ispreferably adjusted such that the total amount of the diamine compoundis from 0.5% by mole to 1.5% by mole, and more preferably from 0.9% bymole to 1.1% by mole, with respect to 1% by mole of the total amount ofthe acid anhydride.

The reaction of the diamine compound with the acid anhydride ispreferably carried out in an organic solvent.

The organic solvent is not particularly limited, as long as the solventdoes not react with the diamine compound according to the presentinvention and with the acid anhydride, and capable of dissolving thereaction product of the diamine compound with the acid anhydride.Examples of such an organic solvent include N-methyl-2-pyrrolidone,N,N-dimethylformamide, N,N-dimethylacetamide,N,N′-dimethylimidazolidinone, γ-butyrolactone, dimethyl sulfoxide,sulfolane, 1,3-dioxolane, tetrahydrofuran, ethylene glycol monobutylether, ethylene glycol monoethyl ether, propylene glycol monomethylether, propylene glycol monoethyl ether, ethylene glycol dimethyl ether,ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethyleneglycol dimethyl ether, diethylene glycol diethyl ether, diethyleneglycol methyl ethyl ether, dipropylene glycol dimethyl ether, diethyleneglycol dibutyl ether, dibenzyl ether, ethylene glycol monoethyl etheracetate, diethylene glycol monobutyl ether acetate, propylene glycolmonomethyl ether acetate, propyl acetate, propylene glycol diacetate,butyl acetate, isobutyl acetate, 3-methoxybutyl acetate,3-methyl-3-methoxybutyl acetate, benzyl acetate, butylcarbitol acetate,methyl lactate, ethyl lactate, butyl lactate, methyl benzoate, ethylbenzoate, triglyme, tetraglyme, acetylacetone, methyl propyl ketone,methyl butyl ketone, methyl isobutyl ketone, cyclopentanone,2-heptanone, butyl alcohol, isobutyl alcohol, pentanol,4-methyl-2-pentanol, 3-methyl-2-butanol, 3-methyl-3-methoxybutanol,diacetone alcohol, toluene and xylene.

From the viewpoint of improving the solubility of the polyimide compoundaccording to the present invention, N-methyl-2-pyrrolidone,N,N′-dimethylimidazolidinone, γ-butyrolactone are preferred.

The diamine compound and the acid anhydride are preferably reacted at areaction temperature of 40° C. or lower, in the case of carrying out thereaction by chemical imidization. In the case of carrying out thereaction by thermal imidization, in contrast, the reaction temperatureis preferably from 150 to 220° C., and more preferably from 170 to 200°C.

When carrying out the cyclodehydration reaction, an imidization catalystmay be used. Examples of the imidization catalyst which can be usedinclude: methylamine, ethylamine, trimethylamine, triethylamine,propylamine, tripropylamine, butylamine, tributylamine, tert-butylamine,hexylamine, triethanolamine, N,N-dimethylethanolamine,N,N-diethylethanolamine, triethylenediamine, N-methylpyrrolidine,N-ethylpyrrolidine, aniline, benzylamine, toluidine, trichloroaniline,pyridine, collidine, lutidine, picoline, quinolone, isoquinolone, andvalerolactone.

Further, it is possible to use, as necessary, an azeotropic dehydratingagent, such as toluene, xylene or ethylcyclohexane, or an acid catalyst,such as acetic anhydride, propionic anhydride, butyric anhydride orbenzoic acid anhydride.

In the reaction of the diamine compound with the acid anhydride, it ispossible to use an end capping agent, such as benzoic acid, phthalicanhydride or hydrogenated phthalic anhydride.

Further, it is also possible to introduce a double bond or a triple bondat an end of the polyimide compound, by using, for example, maleicanhydride, ethynylphthalic anhydride, methylethynylphthalic anhydride,phenylethynylphthalic anhydride, phenylethynyltrimellitic anhydride, 3-or 4-ethynylaniline, or the like.

By introducing a double bond or a triple bond to the polyimide compound,the polyimide compound according to the present invention can be used asa thermosetting resin.

Molded Product

The molded product according to the present invention includes thepolyimide compound obtained using the diamine compound represented bythe general formula (1).

Examples of the molded article including the polyimide include:automotive parts such as cylinder head covers, bearing retainers, intakemanifolds and pedals; casings and electronic material parts such asflexible printed circuit boards and printed wiring boards, used inpersonal computers and mobile phones; and fuel cell parts such asion-conductive separators.

The shape of the molded product according to the present invention isnot particularly limited, and it can be changed as appropriate,depending on the application thereof. For example, the molded productcan be formed in the form of a film or a sheet.

In the molded product according to the present invention, the content ofthe polyimide compound obtained using the diamine compound representedby the general formula (1) is preferably 30% by mass or more and 100% bymass or less, more preferably 50% by mass or more and 100% by mass orless, and still more preferably 60% by mass or more and 100% by mass orless.

The molded product according to the present invention may includeanother compound to the extent that the properties of the molded productare not impaired. Examples of the other compound include polyolefinresins, polyester resins, cellulose resins, vinyl resins, polycarbonateresins, polyamide resins, styrene resins, and ionomer resins.

Further, the molded product according to the present invention maycontain various types of additives, to the extent that the properties ofthe molded product are not impaired. Examples of the additives include:plasticizers, UV light stabilizers, stain inhibitors, matting agents,deodorants, flame retardants, weather resistant agents, antistaticagents, yarn friction reducing agents, slip agents, mold release agents,antioxidants, ion exchangers, dispersants and UV absorbers; andcolorants such as pigments and dyes.

The molded product according to the present invention preferably has a5% by weight reduction temperature of 350° C. or higher, and morepreferably 400° C. or higher.

In the present invention, the 5% by weight reduction temperature of themolded product can be measured in accordance with JIS K 7120, using athermomechanical analyzer (for example, TGA-50 (brand name);manufactured by Shimadzu Corporation) in nitrogen and at a temperaturerise rate of 5° C./min.

The molded product according to the present invention preferably has aglass transition temperature (Tg) of 180° C. or higher, more preferably190° C. or higher, and still more preferably 200° C. or higher.

n the present invention, the glass transition temperature (Tg) of themolded product can be measured in accordance with JIS K 7121, using athermomechanical analyzer (brand name: DSC-60 Plus; manufactured byShimadzu Corporation) under a stream of nitrogen gas and at atemperature rise rate of 10° C./min.

The molded product according to the present invention preferably has amelting temperature of 150° C. or higher, and more preferably 200° C. orhigher. Further, the molded product has a melting temperature of 420° C.or lower, and more preferably 370° C. or lower.

In the present invention, the melting temperature of the molded productcan be measured by a DSC measuring apparatus and/or a dynamicviscoelasticity measuring device.

The molded product according to the present invention preferably has athermal expansion coefficient (CTE) of 70.0×10⁻⁶/K or less, morepreferably 65.0×10⁻⁶/K or less, and still more preferably 60.0×10⁻⁶/K orless.

In the present invention, the thermal expansion coefficient (CTE) of themolded product refers to the average thermal expansion coefficient (CTE)in the temperature range of from 100° C. to 250° C. Specifically, theaverage thermal expansion coefficient (CTE) is obtained by: heating themolded product from room temperature to 450° C. at a temperature riserate of 10° C./min, using TMA-60 (brand name) manufactured by ShimadzuCorporation, while adding a load of 5 g thereto; and calculating theaverage value of the thermal expansion coefficients measured in thetemperature range of from 100° C. to 250° C.

The molded product according to the present invention preferably has atensile strength of 45 MPa or more, and more preferably 50 MPa or more,and still more preferably 60 MPa or more.

In the present invention, the tensile strength of the molded productrefers to the average value of the tensile strengths in the MD directionand in the TD direction of the molded product, measured using a tensiletester (brand name: AG-X plus 50 kN; manufactured by ShimadzuCorporation) at a tensile speed of 10 mm/min.

The molded product according to the present invention preferably has anelastic modulus of 2.5 GPa or more, more preferably 3.0 GPa or more, andstill more preferably 3.5 GPa.

The elastic modulus of the molded product according to the presentinvention refers to the average value of the elastic moduli in the MDdirection and in the TD direction of the molded product, measured usinga tensile tester (brand name: AG-X plus 50 kN; manufactured by ShimadzuCorporation) at a tensile speed of 10 mm/min.

The molded product according to the present invention preferably has awater absorption rate of 1.5% or less, and more preferably 1.0% or less.

The water absorption rate of the molded product according to the presentinvention can be obtained as follows. Specifically, the molded productis dipped in distilled water for 24 hours; water adhered to the surfaceof the molded product is wiped off with a waste cloth, followed bymeasuring the weight thereof; then the molded product is dried at 120°C. for 2 hours, followed by measuring the weight thereof; andcalculating the rate of reduction in weight, to obtain the waterabsorption rate of the molded product.

Method of Producing Molded Product

In one embodiment, the molded product according to the present inventioncan be produced by dissolving the above described polyimide compound inthe organic solvent, such as N-methyl-2-pyrrolidone (NMP), and coatingthe resulting solution on a substrate, such as a copper foil, followedby drying. In this manner, the molded product in the form of a film canbe obtained.

Further, the substrate may be peeled off from the molded product, or thesubstrate may be removed by carrying out an etching treatment, dependingon the application.

The molded product including the polyimide compound according to thepresent invention can be produced by a method consisting of the stepsof: coating a polyisoimide compound or the polyimide compound on asubstrate; and drying the coated compound. Accordingly, it is possibleto omit a heat drying step which has been carried out in a conventionalmethod, and which involves an imidization reaction and is performed at ahigh temperature. In addition, since the heat drying step can beomitted, it is possible to form the molded product according to thepresent invention on any of various types of substrates, without takinginto consideration the heat resistance of the substrate.

Further, the molded product according to the present invention can beproduced by a conventionally known method, such as press molding,transfer molding, injection molding or the like.

In another embodiment, the molded product according to the presentinvention can also be produced by a conventional method in which apolyamic acid solution or a polyisoimide solution is used.

For example, the diamine compound represented by the general formula (1)is allowed to react with the acid anhydride, suitably for a period offrom 2 to 24 hours, while maintaining the temperature at 40° C. orlower, suitably within the range of from 0 to 25° C., and stirring thecompounds in an organic solvent, to obtain a polyamic acid solution. Theresulting polyamic acid solution is coated on a desired substrate (suchas a copper foil), and the coated substrate is heat dried at a finaldrying temperature of from 250 to 450° C., more suitably from 350 to400° C., to carry out imidization of the resulting polyamic acidcompound. In this manner, a molded product including the polyimidecompound according to the present invention can be formed on thesubstrate.

Further, the polyisoimide solution can be prepared by adding adehydration condensation agent, such as N,N′-dicyclohexylcarbodiimide ortrifluoroacetic anhydride, to the polyamic acid solution. By coating thethus prepared polyisoimide solution on a substrate, and heat drying thecoated substrate, it is possible to form a molded product including thepolyimide compound according to the present invention on the substrate.

In cases where N,N′-dicyclohexylcarbodiimide is used, it is preferred toremove N′-dicyclohexylurea generated in the reaction by filtration.Further, in cases where trifluoroacetic anhydride is used, it ispreferred to use a poor solvent, such as methanol, in the isolation andpurification of the polyisoimide compound. The isolated and purifiedpolyisoimide compound can be thermally converted into a polyimidecompound, by heating the polyisoimide compound at a temperature of 140°C. or higher, more preferably at a temperature of 180° C. or higher.

EXAMPLES Example 1-1 Synthesis of Diamine Compound

To a 1 L four-necked flask equipped with a thermometer and a stirrer,500 g of toluene, and 51.06 g (0.30 moles) of a commercially availableproduct of o-phenylphenol (manufactured by Wako Pure ChemicalIndustries, Ltd.) were introduced. While cooling the resulting mixtureand maintaining the reaction temperature within the range of from −5 to0° C., 30 g (0.33 moles) of 70% by weight nitric acid (d=1.42) was addeddropwise to the mixture over 2 hours. Further, the resultant was stirredat the same temperature for 3 hours, to complete the reaction.

The slurry of the resulting product was recovered by filtration, andwashed with an aqueous solution of sodium hydrogen carbonate, and thenwith water.

Subsequently, the resultant was dried under reduced pressure, to obtain2-hydroxy-5-aminobiphenyl represented by the following formula (5),having a color of pale yellow to yellow.

The purity of the resulting compound as measured by HPLC analysis (area%) was 97.01%, and the melting point as measured by DSC was 128° C.(endothermic peak). The analysis results were as follows: ¹H-NMR (CDCl3)σ 5.84 ppm (1H of OH of phenol), σ 6.99 ppm (1H of o-position ofphenol), σ 7.15 to 7.50 ppm (5H of o-phenyl), and σ 8.12 to 8.20 ppm (2Hof m-position of phenol). The results confirmed that a nitro group wasintroduced at the p-position of phenol.

To a 1 L four-necked flask equipped with a thermometer, a stirrer and areflux condenser, 43.04 g (0.20 moles) of 2-hydroxy-5-nitrobiphenylsynthesized as descried above, and 45.53 g (0.24 moles) of acommercially available product of 4-nitrobenzoyl chloride represented bythe following formula (6), and 500 g of N,N′-dimethylformamide wereintroduced, and the resulting mixture was stirred while maintaining thetemperature at approximately 15° C.

Subsequently, 30.36 g (0.30 moles) of triethylamine was slowly added tothe mixture. After the completion of the addition, the reaction wasallowed to proceed for 3 hours, while heating at 50° C. After thecompletion of the reaction, the reaction mixture was cooled to 25° C.,and ion exchanged water was introduced thereinto, to obtainprecipitates. After the temperature of the resultant reached 25° C., theprecipitates were recovered by filtration, and washed with methanol andwith ion exchanged water for a plurality of times, respectively. Thewashed precipitates were then dried under reduced pressure, to obtain acompound represented by the following formula (10).

To a 500 cc autoclave equipped with a thermometer and a stirrer, 22 g(0.06 moles) of the compound represented by the chemical formula (10),150 ml of dimethylacetamide, 5% Pd-carbon (as a dried product) wereintroduced, and the autoclave was replaced with nitrogen, and thenreplaced with hydrogen.

The compounds were then reduced, while maintaining the autoclave at ahydrogen pressure of 9 kg/cm2 (gauge pressure) and a temperature of 80°C., and the absorption of hydrogen stopped approximately after 2 hours.Further, the resultant was matured for 1 hour at 80° C., and then cooledto room temperature. After replacing the autoclave with nitrogen, thesolution of the generated product was recovered, and the catalystcontained therein was removed by filtration. The filtrate was introducedinto 50% methanol to allow precipitation of crystals, and the resultingcrystals were collected.

The crystals were dried at 50° C. under vacuum, to obtain a diaminecompound which satisfies the general formula (1) and which isrepresented by the following chemical formula (2). The purity of theresulting compound as measured by HPLC analysis (area %) was 99.04%, andthe melting point as measured by DSC was 154° C. (endothermic peak).

Further, ¹H-NMR, ¹³C-NMR, FT-IR and elemental analysis were carried outto identify the resulting compound and to confirm the structure thereof.As a result, it has been confirmed that the thus obtained compound was acompound represented by the chemical formula (2). The results of ¹H-NMR(300 MHz; measuring apparatus: Varian 300-MR spectrometer; heavysolvent: DMSO-d₆), ¹³C-NMR (75 MHz; measuring apparatus: Varian 300-MRspectrometer; heavy solvent: DMSO-d₆) and FT-IR (KBr method; measuringapparatus: FTIR-410 spectrometer) are shown in FIGS. 1 to 3.

Synthesis of Polyimide Compound

To a 500 ml separable flask equipped with a nitrogen-introducing pipeand a stirring apparatus, 9.13 g (30 millimoles) of the diamine compoundobtained as described above and represented by the chemical formula (2),15.61 g (30 millimoles) of4,4′-(4,4′-isopropylidenediphenoxy)bisphthalic dianhydride, 94.64 g ofN-methyl-2-pyrrolidone, 0.47 g (6 millimoles) of pyridine, and 10 g oftoluene were introduced. The resulting mixture was allowed to react for4 hours at 180° C. under a nitrogen atmosphere, while removing tolueneout of the system, during the reaction, to obtain 20% by weight of apolyimide solution. In the thus obtained polyimide solution,precipitation of the synthesized polyimide compound was not observed. Inthe DSC measurement, the glass transition temperature was observed at207° C., and the synthesized polyimide compound was found to be anamorphous polyimide.

Example 1-2 Synthesis of Polyimide Compound

The same procedure as in Example 1-1 was repeated except that 10.75 g(30 millimoles) of 3,3′,4,4′-biphenylsulfonetetracarboxylic dianhydridewas used instead of 4,4′-(4,4′-isopropylidenediphenoxy)bisphthalicdianhydride, and N-methyl-2-pyrrolidone was used in an amount of 75.20g, to obtain 20% by weight of a polyimide solution. In the thus obtainedpolyimide solution, precipitation of the synthesized polyimide compoundwas not observed. In the DSC measurement, an endothermic peak wasobserved at 271° C., and the synthesized polyimide compound was found tobe a semicrystalline polyimide.

Comparative Example 1-1 Synthesis of Polyimide Compound

The same procedure as in Example 1-1 was repeated except that 6.85 g (30millimoles) of 4-aminophenyl-4-aminobenzoate represented by thefollowing formula was used instead of the diamine compound representedby the chemical formula (2), and N-methyl-2-pyrrolidone was used in anamount of 85.52 g, to prepare a polyimide solution. However, thesynthesized polyimide compound had precipitated in the polyimidesolution.

Comparative Example 1-2 Synthesis of Polyimide Compound

The same procedure as in Example 1-1 was repeated except that: 6.85 g(30 millimoles) of 4-aminophenyl-4-aminobenzoate was used instead of thediamine compound represented by the chemical formula (2); 10.75 g (30millimoles) of 3,3′,4,4′-biphenylsulfonetetracarboxylic dianhydride wasused instead of 4′-(4,4′-isopropylidenediphenoxy)bisphthalicdianhydride; and N-methyl-2-pyrrolidone was used in an amount of 66.08g; to prepare a polyimide solution. However, the synthesized polyimidecompound had precipitated in the polyimide solution.

Example 2-1 Preparation of Molded Product

To a 500 mL separable flask equipped with a nitrogen-introducing pipeand a stirring apparatus, 8.83 g (30 millimoles) of3,3′,4,4′-biphenyltetracarboxylic dianhydride, 9.13 g (30 millimoles) ofthe diamine compound obtained as described above and represented by thechemical formula (2), and 67.52 g of N-methyl-2-pyrrolidone wereintroduced. The resulting mixture was stirred for 8 hours under anitrogen atmosphere, to obtain 20% by weight of a polyamic acidsolution.

The thus prepared polyamic acid solution was coated on a copper foil bya spin coating method, and dried at 100° C. for 0.5 hours, at 200° C.for 0.5 hours, at 300° C. for 2 hours, and then at 350° C. for 0.5hours. Thereafter, the copper foil was removed by etching, to obtain amolded product in the form of a film having a thickness of about 15 μm.

Example 2-2 Preparation of Molded Product

The same procedure as in Example 2-1 was repeated except that 9.31 g (30millimoles) of bis(3,4-dicarboxyphenyl) ether dianhydride was usedinstead of 3,3′,4,4′-biphenyltetracarboxylic dianhydride, andN-methyl-2-pyrrolidone was used in an amount of 69.44 g, to obtain amolded product in the form of a film having a thickness of about 20 μm.

Reference Example 2-1 Preparation of Molded Product

The same procedure as in Example 2-1 was repeated except that: 6.85 g(30 millimoles) of 4-aminophenyl-4-aminobenzoate represented by thefollowing formula was used instead of the diamine compound representedby the chemical formula (2); 8.83 g (30 millimoles) of3,3′,4,4′-biphenyltetracarboxylic dianhydride was used instead ofpyromellitic dianhydride; and N-methyl-2-pyrrolidone was used in anamount of 58.40 g; to obtain a molded product in the form of a filmhaving a thickness of about 20 μm.

Performance Evaluation of Molded Product 5% by Weight ReductionTemperature

The 5% by weight reduction temperature of each of the molded productsobtained in the above described Examples and Comparative Examples wasmeasured in accordance with JIS K 7120, using TGA-50 (brand name)manufactured by Shimadzu Corporation, in the air and at a temperaturerise rate of 10° C./min. The measurement results are shown in Table 1.

Glass Transition Temperature (Tg)

The glass transition temperature (Tg) of each of the molded productsobtained in the above described Examples and Comparative Examples wasmeasured in accordance with JIS K 7121, using DSC-60 Plus (brand name)and TMA-60 (brand name) manufactured by Shimadzu Corporation, under astream of nitrogen gas and at a temperature rise rate of 10° C./min. Themeasurement results are shown in Table 1.

Melting Temperature

The measurement of the melting temperature was also carried out usingDSC-60 Plus (brand name) manufactured by Shimadzu Corporation and in thesame manner as described above, and the apex of the endothermic peak wasdefined as the melting temperature (Tm). The measurement results areshown in Table 1.

Thermal Expansion Coefficient (CTE)

The molded products obtained in the above described Examples andComparative Examples were each cut into a test piece having a size of 5mm×20 mm. Using TMA-60 (brand name) manufactured by ShimadzuCorporation, each test piece was heated from room temperature to 450° C.at a temperature rise rate of 10° C./min, while applying a load of 5 gthereto, and the average thermal expansion coefficient (CTE) in thetemperature range of from 100° C. to 250° C. was calculated for eachtest piece. The results are shown in Table 1.

Tensile Strength

The molded products obtained in the above described Examples andComparative Examples were each cut into a test piece having a size of 10mm×80 mm. Using a tensile tester (brand name: AG-X plus 50 kN;manufactured by Shimadzu Corporation), the tensile strength in the MDdirection and the tensile strength in the TD direction of each testpiece were measured, at a tensile speed of 10 mm/min. The average valueof the tensile strength in the MD direction and the tensile strength inthe TD direction was calculated for each test piece, and the results areshown in Table 1.

Elastic Modulus

The molded products obtained in the above described Examples andComparative Examples were each cut into a test piece having a size of 10mm×80 mm. Using a tensile tester (brand name: AG-X plus 50 kN;manufactured by Shimadzu Corporation), the elastic modulus in the MDdirection and the elastic modulus in the TD direction of each test piecewere measured, at a tensile speed of 10 mm/min. The average value of theelastic modulus in the

MD direction and the elastic modulus in the TD direction was calculatedfor each test piece, and the results are shown in Table 1.

Water Absorption Rate

The molded products obtained in the above described Examples andComparative Examples were each cut into a test piece having a size of 50mm×50 mm. Each test piece was dipped in distilled water for 24 hours,and after wiping off water adhered to the surface with a waste cloth,the weight of the test piece was measured. Subsequently, the test piecewas dried at 120° C. for 2 hours, and the weight of the dried moldedproduct was measured. The absorption rate of each test piece wasdetermined from the rate of reduction in weight, and the results areshown in Table 1.

As is evident from Table 1, it has been found out that each of themolded products produced using the polyimide compound according to thepresent invention has a 5% by weight reduction temperature, a thermalexpansion coefficient, a tensile strength, an elastic modulus and awater absorption rate, which are comparable to those of a molded productproduced using a conventionally known polyimide compound, as well as ahigh heat resistance and high mechanical properties.

Further, it has become possible to produce a polyimide having a meltingpoint, which is difficult to achieve by a conventional polyimide. Thisenabled the production of a highly heat resistant polyimide moldedproduct which can be produced by melt molding, such as extrusion moldingor injection molding.

TABLE 1 5% by weight Thermal Water reduction Glass transition Meltingexpansion Tensile Elastic absorption Temperature temperature temperaturecoefficient strength modulus rate (° C.) (° C.) (° C.) (10⁻⁶/K) (MPa)(GPa) (%) Example 2-1 517 262 360 10.3 182 8.5 0.4 Example 2-2 506 229411 23.6 105 5.4 0.3 Reference 566 — — 5.6 273 10.2 0.4 Example 2-1

Example 3-1 Synthesis of Polyimide Compound

To a 500 ml separable flask equipped with a nitrogen-introducing pipeand a stirring apparatus, 30.43 g (100 millimoles) of the diaminecompound obtained as described above, 44.43 g (100 millimoles) of anacid anhydride A represented by the following formula, 285 g ofN-methyl-2-pyrrolidone, 1.6 g (20 millimoles) of pyridine, and 30 g oftoluene were introduced. The resulting mixture was allowed to react for6 hours at 180° C. under a nitrogen atmosphere, while removing tolueneout of the system, during the reaction, to obtain 20% by weight of apolyimide solution. In the thus obtained polyimide solution,precipitation of the synthesized polyimide compound was not observed. Inthe DSC measurement, the glass transition temperature was observed at258° C., and the synthesized polyimide compound was found to be anamorphous polyimide.

Example 3-2 Synthesis of Polyimide Compound

The same procedure as in Example 3-1 was repeated except that an acidanhydride B represented by the following formula was used instead of theacid anhydride A, to obtain a polyimide solution. In the thus obtainedpolyimide solution, precipitation of the synthesized polyimide compoundwas not observed. In the DSC measurement, the glass transitiontemperature was observed at 258° C., and the synthesized polyimidecompound was found to be an amorphous polyimide.

Example 3-3 Synthesis of Polyimide Compound

The same procedure as in Example 3-1 was repeated except that an acidanhydride C represented by the following formula was used instead of theacid anhydride A, to obtain a polyimide solution. In the thus obtainedpolyimide solution, precipitation of the synthesized polyimide compoundwas not observed. In the DSC measurement, the glass transitiontemperature was observed at 181° C., and the synthesized polyimidecompound was found to be an amorphous polyimide.

Example 3-4 Synthesis of Polyimide Compound

The same procedure as in Example 3-1 was repeated except that an acidanhydride D represented by the following formula was used instead of theacid anhydride A, to obtain a polyimide solution. In the thus obtainedpolyimide solution, precipitation of the synthesized polyimide compoundwas not observed. In the DSC measurement, the glass transitiontemperature was observed at 231° C., and the synthesized polyimidecompound was found to be an amorphous polyimide.

Example 3-5 Synthesis of Polyimide Compound

The same procedure as in Example 3-1 was repeated except that an acidanhydride E represented by the following formula was used instead of theacid anhydride A, to obtain a polyimide solution. In the thus obtainedpolyimide solution, precipitation of the synthesized polyimide compoundwas not observed. In the DSC measurement, the glass transitiontemperature was observed at 253° C., and the synthesized polyimidecompound was found to be an amorphous polyimide.

Example 4-1 Preparation of Molded Product

The polyimide acid solution prepared in Example 3-1 was coated on acopper foil by a spin coating method, and dried at 100° C. for 0.5hours, at 200° C. for 0.5 hours, and then at 250° C. for 1 hour.Thereafter, the copper foil was removed by etching, to obtain a moldedproduct in the form of a film having a thickness of about 15 μm.

Example 4-2 Preparation of Molded Product

The same procedure as in Example 3-1 was repeated except that thepolyimide acid solution obtained in Example 3-2 was used as thepolyimide acid solution, to obtain a molded product in the form of afilm.

Example 4-3 Preparation of Molded Product

The same procedure as in Example 3-1 was repeated except that thepolyimide acid solution obtained in Example 3-3 was used as thepolyimide acid solution, to obtain a molded product in the form of afilm.

Example 4-4 Preparation of Molded Product

The same procedure as in Example 3-1 was repeated except that thepolyimide acid solution obtained in Example 3-4 was used as thepolyimide acid solution, to obtain a molded product in the form of afilm.

Example 4-5 Preparation of Molded Product

The same procedure as in Example 3-1 was repeated except that thepolyimide acid solution obtained in Example 3-5 was used as thepolyimide acid solution, to obtain a molded product in the form of afilm.

Performance Evaluation of Molded Product

The 5% by weight reduction temperature, the glass transition temperature(Tg), the thermal expansion coefficient (CTE), the tensile strength andthe elastic modulus of each of the molded products were measured in thesame manner as described above, and the results are shown in Table 2.

TABLE 2 5% by weight reduction Glass transition Thermal expansionTensile Elastic Temperature temperature coefficient strength modulus (°C.) (° C.) (10⁻⁶/K) (MPa) (GPa) Example 4-1 488 258 56 58 3.2 Example4-2 463 258 61 105 3.3 Example 4-3 415 181 67 46 3.3 Example 4-4 445 23165 117 2.9 Example 4-5 437 253 66 99 3.1

Example 5-1 Preparation of Molded Product

To a 500 mL separable flask equipped with a nitrogen-introducing pipeand a stirring apparatus, 32.22 g (100 millimoles) of an acid anhydrideF represented by the following formula, 30.43 g (100 millimoles) of thediamine compound obtained in the above described Reference Example, and236 g of N-methyl-2-pyrrolidone were introduced. The resulting mixturewas allowed to react for 8 hours under a nitrogen atmosphere, to obtain20% by weight of a polyamide acid solution.

The thus obtained polyamide acid solution was coated on a copper foil bya spin coating method, and dried at 100° C. for 0.5 hours, at 200° C.for 0.5 hours, at 300° C. for 1 hour, and then at 350° C. for 0.5 hours.Thereafter, the copper foil was removed by etching, to obtain a moldedproduct in the form of a film having a thickness of about 15 μm.

Example 5-2 Preparation of Molded Product Including Polyimide Compound

The same procedure as in Example 5-1 was repeated except that an acidanhydride G represented by the following formula was used instead of theacid anhydride F, to obtain a molded product in the form of a film.

Example 5-3 Preparation of Molded Product Including Polyimide Compound

The same procedure as in Example 5-1 was repeated except that an acidanhydride H represented by the following formula was used instead of theacid anhydride F, to obtain a molded product in the form of a film.

Example 5-4 Preparation of Molded Product Including Polyimide Compound

The same procedure as in Example 5-1 was repeated except that an acidanhydride I represented by the following formula was used instead of theacid anhydride F, to obtain a molded product in the form of a film.

Example 5-5 Preparation of Molded Product Including Polyimide Compound

The same procedure as in Example 5-1 was repeated except that an acidanhydride J represented by the following formula was used instead of theacid anhydride F, to obtain a molded product in the form of a film.

Example 5-6 Preparation of Molded Product Including Polyimide Compound

The same procedure as in Example 5-1 was repeated except that an acidanhydride K represented by the following formula was used instead of theacid anhydride F, to obtain a molded product in the form of a film.

Performance Evaluation of Molded Product

The 5% by weight reduction temperature, the glass transition temperature(Tg), the melting temperature, the thermal expansion coefficient (CTE),the tensile strength and the elastic modulus of each of the moldedproducts were measured in the same manner as described above, and theresults are shown in Table 3.

TABLE 3 5% by weight Thermal reduction Glass transition Meltingexpansion Temperature temperature temperature coefficient Tensilestrength Elastic modulus (° C.) (° C.) (° C.) (10⁻⁶/K) (MPa) (GPa)Example 5-1 487 289 367 37 126 5.6 Example 5-2 355 — 356 10 130 4.0Example 5-3 466 215 354 20 106 7.2 Example 5-4 477 193 355 24 111 5.7Example 5-5 460 230 331 27 52 5.6 Example 5-6 457 236 355 51 68 6.4

The invention claimed is:
 1. A polyimide compound which is a reactionproduct of the diamine compound represented by the following generalformula (1) with an acid anhydride:

(wherein R₁ to R₈ are each independently selected from the groupconsisting of a hydrogen atom, a fluorine atom, a substituted orunsubstituted alkyl group, and a substituted or unsubstituted aromaticgroup; and at least one of R₁ to R₈ is a substituted or unsubstitutedaromatic group).
 2. The polyimide compound according to claim 1, whereinone or two of R₅ to R₈ is/are (each) a substituted or unsubstitutedaromatic group.
 3. The polyimide compound according to claim 1, whereinone or two of R₅ to R₈ is/are (each) a substituted or unsubstitutedaromatic group, and R₁ to R₈ other than the aromatic group(s) are eachselected from the group consisting of a hydrogen atom, a fluorine atom,and a substituted or unsubstituted alkyl group.
 4. The polyimidecompound according to claim 1, wherein the substituted or unsubstitutedaromatic group has from 5 to 20 carbon atoms.
 5. The polyimide compoundaccording to claim 1, wherein the substituted or unsubstituted aromaticgroup is selected from the group consisting of a phenyl group, amethylphenyl group, a phenoxy group, a benzyl group and a benzyloxygroup.
 6. The polyimide compound according to claim 1, wherein the acidanhydride is represented by the following general formula(e) (8) and/or(9):

(wherein L₁ represents a linking group selected from the following groupof linking groups:

wherein R₉ to R₂₀ are each independently selected from the groupconsisting of a hydrogen atom, a substituted alkyl group and anunsubstituted alkyl group; and * represents a binding position).
 7. Thepolyimide compound according to claim 1, wherein the acid anhydride isrepresented by the following general formula(e) (8) and/or (9):

(wherein L₁ represents a linking group selected from the following groupof linking groups:

wherein X represents a halogen group selected from a fluoro group, achloro group, a bromo group and an iodo group; R₂₁ to R₃₀ are eachindependently selected from the group consisting of a hydrogen atom, asubstituted alkyl group and an unsubstituted alkyl group; and *represents a binding position).